Orifice Flange Union
Orifice flange union for differential pressure flow measurement with orifice plate taps
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Orifice Flange Union

Flowell engineers orifice flange unions for dependable, repeatable differential-pressure (DP) flow measurement with minimal downtime. Whether you’re building a new meter run or upgrading a legacy line, we focus on what protects accuracy long-term: stable plate seating, aligned pressure taps, clean sealing faces, and rugged construction for harsh service.

Need selection help? Use our sizing support or contact us with line size, media, and operating conditions for a fast quote.

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How an Orifice Flange Union Works

An orifice flange union measures flow by creating a known pressure differential across a precision orifice plate. As fluid passes through the plate bore, velocity increases and pressure drops. Dedicated taps capture that differential so flow can be calculated using established DP methodologies.

  • Measurement method: Differential pressure across a precision orifice plate
  • Typical pressure classes: CL150, CL300, CL600, CL900, CL1500
  • Face types: RF (Raised Face) and RTJ (Ring-Type Joint)
  • Taps: Corner, flange, or pipe taps per your standard

Accuracy Starts With Plate Fit and Tap Geometry

Measurement stability depends on plate flatness, bore concentricity, edge quality, and repeatable clamping. We machine and inspect sealing faces and tap features to help maintain consistent differentials and reduce drift over time. If you’re selecting beta ratio and bore size, we’ll align recommendations to your service, line size, range, and allowable pressure loss.

Pair with paddle-type orifice plates and compare other DP primary elements like venturi tubes and flow nozzles.

Materials and Build Options

We support common materials for general service and corrosive environments, with alternates available when required for temperature, chemistry, or sour service.

  • Carbon steel: Cost-effective, general-purpose service
  • Stainless steel (304/316): Corrosion resistance for aggressive media
  • Special alloys (on request): For high temperature or unique chemistries

Need custom configurations or machining support? We can help through custom machine work.

Fast Installation and Easy Plate Access

Union-style designs simplify access for inspection, replacement, and re-ranging. Clear orientation markings and practical field serviceability reduce downtime during turnarounds and maintenance windows.

Request a Quote Get Sizing Help

Typical Applications

Orifice flange unions are commonly used anywhere rugged DP flow measurement is required:

  • Oil & Gas: Fuel gas, gathering, produced water, flare and vent monitoring
  • Chemical & Petrochemical: Process control loops and utility services
  • Power generation: Steam, condensate, boiler feedwater support services
  • Water & wastewater: Process monitoring and chemical dosing
  • Industrial facilities: Compressed air, nitrogen, and process liquids

How to Specify Your Orifice Flange Union

Send the details below and we’ll confirm the right configuration and plate sizing approach.

  1. Line size & schedule (or internal diameter)
  2. Pressure class (CL150–CL1500)
  3. Face type (RF or RTJ)
  4. Material (carbon steel, 304/316, etc.)
  5. Tap style (corner, flange, or pipe taps)
  6. Orifice plate details (bore, beta ratio, thickness, style)
  7. Process conditions (media, temperature, pressure, density/viscosity)
  8. Applicable standard / methodology (your site or project requirement)

Technical Snapshot

Parameter Typical Range / Option Notes
Nominal Sizes 1/2″ to 24″+ Larger sizes available upon request
Pressure Classes CL150–CL1500 Match to ASME piping requirements
Face Type RF, RTJ Match to mating flanges and sealing needs
Materials CS, 304/316 SS, alloys Material test reports available on request
Tapping Corner / flange / pipe taps Aligned to common practices and site standards
Orifice Plate Paddle-type See paddle-type orifice plates

Standards Reference

DP flow measurement practices vary by industry and application. If your project references AGA methodologies for gas measurement, see American Gas Association (AGA) resources for standards and guidance.

Orifice Flange Union FAQs

What is an orifice flange union?

An orifice flange union is a flange pair with pressure taps designed to hold an orifice plate between the faces. The pressure differential across the plate is used to calculate flow rate.

How do I choose the correct beta ratio?

Beta ratio (β = d/D) depends on line size, flow range, allowable pressure loss, and instrument range. Send your process data and we’ll recommend a bore size aligned to your methodology and constraints.

Do I need RF or RTJ faces?

It depends on pressure class, temperature, and site practice. RTJ is common at higher pressure classes for enhanced sealing, while RF is widely used in general service. We’ll help match face type to your application.

Can I replace the orifice plate without disturbing the line?

Yes. The union-style configuration is intended to simplify access for inspection or replacement so you can minimize downtime during maintenance.

What information should I send for a quote?

Send line size/schedule, pressure class, face type (RF/RTJ), media, operating temperature/pressure, and desired flow range. If you have a preferred plate style or standard, include that too.

Request a Quote

Send your line size, pressure class, media, temperature, and target flow range and we’ll recommend the right orifice flange union configuration. Contact Flowell.